A teenager has admitted carrying out the frenzied knife attacks on two members of the public which sent "shockwaves" through a quiet garrison town.

The boy, who cannot be named for legal reasons, was just 15 years old when he stabbed James Attfield, 33, more than 100 times in Colchester on March 29 2014.

Mr Attfield, who had a brain injury after being hit by a car four years before, was found fighting for his life in the town's Castle Park in the early hours of the morning. He died later in hospital.

Three months later, the boy knifed Saudi student Nahid Almanea, 31, 16 times as she walked from her student accommodation along the Salary Brook Trail towards the University of Essex on the morning of June 17 2014.

Ms Almanea was captured on CCTV shortly before the attack wearing a Muslim gown called an abaya.

The two deaths sparked fears a killer was randomly striking after police said there were "striking similarities" in the killings but nothing to link the victims.

The teenager, from Colchester, was arrested after allegedly being found with a lock knife on May 26 last year in the same area where Ms Almanea was killed.

During a hearing at the Old Bailey, the youth, now 17, denied two counts of murder and possessing an offensive weapon but admitted two alternative counts of manslaughter by reason of diminished responsibility.

Mr Justice Spencer allowed the prosecution time to consider the pleas.

A murder trial has already been fixed to start on April 11 at a venue to be decided, either in Guildford or central London.

A tearful couple, believed to be the boy's parents, sat in the well of the court and blew him a kiss as he sat flanked by officers in the dock.

The defendant, who wore a grey suit, leather jacket and black rimmed spectacles, spoke only to enter his pleas and confirm his name. He was remanded in custody.

Following the hearing, Detective Chief Inspector Morgan Cronin, of the Kent and Essex Serious Crime Directorate, said: "We hope that today's guilty plea will provide the families of James Attfield and Nahid Almanea with some comfort by finally establishing who carried out their atrocious killings.

"The brutal manner in which they both died sent shockwaves through the community in Colchester and far beyond.

"At its height more than 100 detectives, uniformed officers, PCSOs and civilian staff were involved in these investigations and the response of Essex Police to keep people safe.

"Detectives worked tirelessly to piece together the evidence of how they died and to establish whether there was any connection between their deaths.

"Sadly we now know that one person, a 17-year-old boy, was indeed responsible. I would like to thank everyone who played a part in our investigations, and also pay tribute to the people of Colchester who supported us throughout this difficult time."